Conductive level measurement circuit for minimum-maximum controller

摘要

The circuit includes a probe (S) with three electrodes (19,20,21), an a.c. power supply (W), and an evaluation circuit (A). One probe electrode (20) is connected to the output of the a.c. supply, another probe (21) to a reference potential and the remaining probe (19) to the evaluation circuit. The tapping (47) of a probe reference voltage divider (R) connected between the supply and reference voltage electrodes is connected to the evaluation circuit. The evaluation circuit performs phase selective evaluation of the difference signal between the potential divider tapping and the evaluation circuit connected probe electrode to discretely determine the level. A series resistance can be connected between the generator output and the a.c. supply connected electrode.